RFID devices are known in the art, such as disclosed in U.S. Pat. No. 5,347,263. These devices are used in systems for access control, animal feeding and health programs, inventory control, process control, and security applications.
A typical RFID system has a passive RFID label including RFID circuitry therein and a separate RFID reader/writer. The RFID reader/writer energizes the RFID circuitry by transmitting a power signal. The power signal may convey data which is stored in memory incorporated in the RFID circuitry. In response to the power signal the RFID circuitry may transmit a response signal containing data stored in its memory. The RFID reader/writer receives the response signal and interprets the data contained therein. The data is then transmitted to a host computer for processing.
RFID labels do not function properly when they are in very close proximity to metal. The metal attenuates the response signal from the RFID circuitry and reduces the read range, i.e. the distance from which the RFID reader/writer can receive the response signal, of the RFID label. In order to minimize the interference caused by a metal supporting surface, a spacer layer forming part of the RFID label is often used. The spacer layer is typically a piece of die cut foam adhesively fixed to a substrate on which the RFID circuitry is disposed. The spacer layer spaces the RFID circuitry from the metal supporting surface to increase the read range of the RFID label. Unfortunately, the thickness of the spacer layer often causes the RFID label to jam when used in a printer. As a result, RFID labels for use on metal support surfaces are often fed through a printer prior to affixing a spacer layer. This added step of affixing the spacer layer after printing reduces the usefulness of the RFID label and increases the cost of use.